1. Field of the Invention
The present invention pertains to a method and apparatus for removing particles adhering to a semiconductor wafer. More specifically, the present invention comprises an improved method and apparatus for removing particles on a semiconductor wafer employing a combination of brush scrubbing processing and jet water cleaning, while immersing both the brush and the wafer in water; as well as optional application of ultrasonic waves to the water during the cleaning.
2. Description of the Related Art
With the higher density and finer geometry of integrated circuits to be formed on a semiconductor wafer, even particles as small as about 0.3 .mu.m have a considerable effect on the yield of products. Because of this, the semiconductor industry has been placing more and more importance on techniques for removing particles from the surface of a semiconductor wafer. Needless to say, it is vital to develop an improved technique which is simple and is still able to remove particles as efficiently as possible while keeping the cleaning time short.
As an example of conventional particle removing techniques, the invention disclosed in Japanese Patent Laid Open Application No. 31780/96 can be cited. The method described therein comprises the removal of particles by directing, from one direction, a jet stream of pure water against the surface of a rotating semiconductor substrate while pressing a rotating brush against the surface of the substrate and moving the brush in a predetermined manner.
FIGS. 1 and 2, respectively, are a perspective and a front view of a prior art particle removing apparatus. A typical prior art procedure for removing particles using the prior art apparatus of FIGS. 1 and 2 is as follows.
First, wafer 3, on which a resist etch back processing has been performed, is mounted on wafer support 5. Wafer 3 is made to rotate while jet stream discharge pipe 10 directs a first jet stream consisting of pure water against wafer 3. Next, brush 2 is brought into contact with the surface of the wafer, where brush 2 rotates to move from side to side. After a predetermined period of time, brush 2 is moved out of contact with wafer 3 and the surface of wafer 3 is rinsed with another jet stream (second jet stream) consisting of pure water to thereby discharge pure water 4 containing particles.
Table 1 below indicates the results of an experiment conducted by the present inventors, which shows the numbers of particles (not smaller than 0.3 .mu.m) on wafer 3 before the above-described prior art processing and after performing the prior art processing for various predetermined different time periods.
TABLE 1 Particles on Wafer Particles on Wafer Before Processing After Processing Processing Time 300 101 1 minute of first jet stream + 1 minute of scrubbing + 1 minute of second jet stream 312 89 1 minute of first jet stream + 2 minutes of scrubbing + 1 minute of second jet stream 305 72 1 minute of first jet stream + 2 minutes of scrubbing + 2 minutes of second jet stream
As is clear from the results shown in Table 1, while the number of particles before the above described prior art processing is not less than 300, the number of particles after the prior art processing is still as high as 100.